The present invention relates to a piezoelectric device, an ink-jet head using the same, and a process for producing the same.
The conventional actuator that can typically be used as a drive mechanism for an ink-jet head that ejects ink droplets or as a pressure sensor is a piezoelectric device that uses a piezoelectric film which expands or contracts according as the applied voltage varies. The piezoelectric device has a lower electrode, the piezoelectric film and an upper electrode that are superposed on an Si— or otherwise formed substrate, and by applying voltage to it from the lower and upper electrodes, the piezoelectric film is allowed to expand or contract.
An example of this piezoelectric device is described in JP 3849773 B and it is fabricated by the steps of patterning a lower electrode 60 to form an overall pattern, then forming a piezoelectric film layer and an upper electrode film layer by the sol-gel method, sputtering or the like, and selectively etching the piezoelectric film layer and the upper electrode film layer to provide a desired pattern for the piezoelectric device.
In subsequent steps, an adhering layer and an overlying layer are formed on top of the upper electrode film layer and after forming a mask layer that serves as a mask pattern, the overlying layer is selectively removed by dry etching and thereafter the adhering layer is removed by wet etching to form lead electrodes on the upper electrode film layer.
JP 2004-186646 A describes a piezoelectric device in which an electrically conductive material such as Pt is deposited to a thickness of 0.1 μm to 0.4 μm on a second electrode layer that serves as the lower electrode.